Improve description of "Channel Count" option

1) Indicate how many audio channels each choice represents, for example: Low (16), Medium (32), High (64), Very High (128). Currently we have to guess what each choice stands for.

2) Add a ? tooltip button beside it that clarifies that higher values can decrease performance (if an audio hardware solution without a dedicated SPU is utilized) and that higher values may result in some missing audio if your audio device doesn't support it (assuming the games audio mixing is handled by hardware instead of software).

Practically all audio devices (including integrated audio) that was released in the last 15 years support 64 channels (so it should probably be the default) while some high-end audio devices like the Soundblaster Z support 128 or more channels.

I really would like to know what each choice means (and being able to be reminded in-game) and whether or not the highest setting will sound fine on my 64 channel integrated audio solution or if I'll be missing some sounds if I choose the highest setting.